An exemplary conventional read/write head comprises a thin film write element with a bottom pole P1 and a top pole P2. The pole P1 has a pole tip height dimension commonly referenced as “throat height”. In a finished write element, the throat height is measured between the ABS and a zero throat level where the pole tip of the write element transitions to a back region. The ABS is formed by lapping and polishing the pole tip. A pole tip region is defined as the region between the ABS and the zero throat level. Similarly, the pole P2 has a pole tip height dimension commonly referred to as “nose length”. In a finished read/write head, the nose is defined as the region of the pole P2 between the ABS and the “flare position” where the pole tip transitions to a back region.
Pole P1 and pole P2 each have a pole tip located in the pole tip region. The tip regions of pole P1 and pole P2 are separated by a recording gap that is a thin layer of non-magnetic material. During a write operation, the magnetic field generated by pole P1 channels the magnetic flux from pole P1 to pole P2 through an intermediary magnetic disk, thereby causing the digital data to be recorded onto the magnetic disk.
The magnetic read/write head is coupled to a rotary actuator magnet and a voice coil assembly by a suspension and an actuator arm positioned over a surface of a spinning magnetic disk. In operation, a lift force is generated by the aerodynamic interaction between the read/write head and the spinning magnetic disk. The lift force is opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disk.
The flying height is defined as the magnetic spacing between the surface of the spinning magnetic disk and the lowest point of the slider assembly. One objective of the design of magnetic read/write heads is to obtain a very small flying height between the read/write element and the disk surface. With the ever increasing areal density, by maintaining a flying height as close to the magnetic disk as practically feasible, it is possible to record short wavelength or high frequency signals, thereby achieving high density and high storage data recording capacity.
A significant design challenge in a conventional read/write head is to achieve an ultra low flying height without causing physical damage to either the slider or the disk that may result in reliability problems and head crashes. Such as damage could cause both accelerated wear and performance degradation. The wear effect is due to the abrasive contact between the slider and the disk, which tends to cause the slider off track, thereby causing errors in the track following capability of the read/write head.
Typically, during operation, the magnetic read/write head is subjected to various mechanical and thermal conditions that tend to compromise the ability to attain the ultra low flying height in a conventional read/write head. For example, ambient pressure variations in the hard disk operating condition may contribute to the flying height variations. Similarly, mechanical disturbances during operation, such as vibration, also pose as a source of difficulty in maintaining the ultra low flying height.
Furthermore, during a typical operation, the magnetic disk spins at a rapid rate of rotation, typically on the order of several thousands revolutions per minute (RPM). This rapid rotation is a source of friction in the ambient air between the ABS and the spinning magnetic disk, causing an elevation in the operation temperature of the read/write head.
Additionally, the read/write head is also subjected to various other thermal sources of power dissipation resulting from the motor heating, current supplied to the write coils, eddy current in the core, and the current in the read sensor. The power dissipation manifests itself as a localized heating of the read/write head, resulting in a further temperature rise of the read/write head.
The combined mechanical and thermal effect therefore generally render the pole tip of the read/write head in a very close proximity to the magnetic disk in an uncontrolled manner that may possibly cause a physical interference of the read/write head.
In an attempt to resolve the foregoing problem, a number of conventional designs of read/write heads incorporate the use of heater coils to control the dynamic flying height of the read/write head.
Although this technology may have proven to be useful in controlling the dynamic flying height of the read/write head, it is still not entirely satisfactory in practice. Due to the reliance on the thermal expansion effect as a means to control the dynamic flying height, the response time is relatively slow. Since the ultra low flying height is typically lower than 12.5 nm, a flying height that is lower than 10 nm could cause a reliability problem.
Therefore, there remains a need for a read/write head that is capable of controlling the ultra low dynamic flying height during a read/write operation without causing undesirable pole tip protrusion during idle flying time. The need for such a design has heretofore remained unsatisfied.